Hoodoo and South Landlocked Bay Mining Co.

Mine, Inactive

Commodities and mineralogy

Main commodities Cu; Zn
Other commodities Ag; Au
Ore minerals chalcopyrite; native copper; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.848
Longitude -146.549
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents a mine and a prospect along the south shore of Landlocked Bay. The map site is at an elevation of about 150 feet, just inland from the bay. It is in the NW1/4 sec. 7, T. 12 S., R. 7 W., of the Copper River Meridian. The site location is accurate to within 2000 ft. This site combines both sites C-70 and C-71 of Jansons and others (1984) and site #15 of Cobb (1972: MF-392). The site location was updated from a 2014 site visit.

Geologic setting

Geologic description

The mineral deposits at this site are in mafic volcanic rocks (greenstone) of the Tertiary Orca Group (Nelson and others, 1985) and consist of massive sulfide lenses in shear zones 1.5 ft. to 3 ft. wide (Jansons and others, 1984). The ore minerals are mainly chalcopyrite and sphalerite; native copper is also reported.
Development work began in 1904 (Cobb, 1979: OFR 79-973). Extensive surface stripping at 230 feet elevation exposed about 75 feet of a 3-foot-wide mineralized zone in metavolcanic rock striking N45W, and dipping 60 NE. Four tunnels were driven, the longest of which was 180 feet (Capps and Johnson, 1913). In 1953 one tunnel was inaccessible (Mihelich and Wells, 1957). Early assays contained 0.48 to 1.06 oz. Au/ton. Recent sampling (Jansons and others, 1984) of five chip samples from one adit contained 0.11 ppm to 2.9 percent Cu, 680 ppm to 0.95 percent Zn, <0.03 to 0.03 parts permillion (ppm) Au, and 0.2 to 13.9 ppm Ag. Three grab samples contained 1.14 percent to 19.3 percent Cu, 0.95 to 2.25 percent Zn, 0.15 ppm to 44 ppm Au, and 0.23 ppm to 34 ppm Ag.
A 2014 grab sample contained 0.075 ppm Au, 39.2 ppm Ag, 8.7 percent Cu, and 3.26 percent Zn (Angel, 2014).
Geologic map unit (-146.551995616924, 60.8494517526402)
Mineral deposit model Cyprus massive sulfide (Cox and SInger, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Tertiary based on the age of the host rocks.
Alteration of deposit Oxidation of copper minerals (Angel, 2014).

Production and reserves

Workings or exploration
Development work began in 1904 (Cobb, 1979: OFR 79-973) Extensive surface stripping at 230 feet elevation exposed about 75 feet of a 3-foot-wide mineralized zone in metavolcanic rock striking N45W, and dipping 60 NE. Four tunnels were driven, the longest of which was 180 feet (Capps and Johnson, 1913). In 1953 one tunnel was inaccessible (Mihelich and Wells, 1957). Early assays contained 0.48 to 1.06 oz. Au/ton. Recent sampling (Jansons and others, 1984) of five chip samples from one adit contained 0.11 parts per million (ppm) to 2.9 percent Cu, 680 ppm to 0.95 percentZn, <0.03 to 0.03 ppm Au, and 0.2 to 13.9 ppm Ag. Three grab samples contained 1.14 percent to 19.3 percent Cu, 0.95 to 2.25 percent Zn, 0.15 ppm to 44 ppm Au, and 0.23 ppm to 34 ppm Ag.
Field work including sampling was performed in 2014. A grab sample contained 0.075 ppm Au, 39.2 ppm Ag, 8.7 percent Cu, and 3.26 percent Zn (Angel, 2014).
Indication of production Yes; small
Reserve estimates Hoodo: inferred reserves of 300 tons @ 1.29 percent Cu, 0.34 percent Zn, and 7.97 ppm Ag. South Landlocked Bay: inferred reserves of 600 tons @ 4.7 percent Cu and 2.6 percent Zn (Jansons and others, 1984).
Production notes None reported from Hoodo. The South Landlocked Bay mine produced 74, 240 lbs. Cu (Mihelich and Wells, 1957).

Additional comments

Crowe and others (1992; 1993) and Sainsbury (1993) discuss the genesis of the volcanogenic massive sulfide deposits in this area.
Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.

References

MRDS Number A010435

References

Angel, A.K., 2014 Mineral Assessment of Chugach Alaska Lands, Unpublished Report, 21p. (Report held by Chugach Alaska Corporation, Anchorage, Alaska).
Reporters S.W. Nelson, Anchorage, AK; A.K. Angel (Alaska Earth Sciences, Inc.)
Last report date 9/8/2014